1. Field of the Invention
The present invention relates to a micro-coaxial cable assembly and a method for making the same, and particularly to a method for stably and conveniently soldering braiding layers of a micro-coaxial cable to a substrate.
2. Description of Related Art
A micro-coaxial cable configured by a plurality of individual wires is usually used for signal transmission between two internal components of a computer. Each individual wire generally includes a core conductor, an inner insulator made from Teflon coated over the core conductor, a metal braiding surrounding the inner insulator for preventing cross talk between adjacent wires, and an outer insulator made from plastic material.
Generally, the micro-coaxial cable is connected with a connector via a transition printed circuit board (PCB). U.S. Pat. No. 5,199,885 discloses a certain type of connector (tradename: MICTOR, manufactured and distributed by AMP Incorporation) which can be used with the micro-coaxial cable. The Mictor connector contains two rows of signal terminals and a grounding bus disposed therebetween. Tails of the signal terminals are arranged in a straddle manner and the grounding bus has a plurality of grounding legs extending between the tails. The transition PCB is formed with conductive pads on top and bottom surfaces for electrical connection with the straddle tails. The PCB is further formed with inner grounding planes to be connected with the grounding legs of the grounding bus of the Mictor connector, as disclosed in the ""885 patent. In addition, the top and bottom surfaces are formed with grounding pads which are interconnected with the grounding planes within the printed circuit board. Before the micro-coaxial cable can be soldered to the transition printed circuit board, it must be subject to certain machining processes, namely 1) stripping the outer insulator to expose the braiding; 2) removing a section of the braiding while leaving a short length thereon; and 3) removing a certain length of the inner insulator to expose the core conductor. After these processes are completed, the core conductors of the micro-coaxial cable are soldered to the conductive pads on the PCB. The braiding layers of the wires are soldered to the grounding pads on the PCB for EMI (Electromagnetic Interference) protection. Thus, a micro-coaxial cable connector assembly is formed.
Before soldering the core conductors and the braiding layers of the wires to the PCB, the conductive and grounding pads of the PCB are individually precoated with solder paste. However, after applying heat to the solder paste, the braiding layer of each wire is connected with the PCB only at a hemline of the braiding layer and a gap between every two adjacent braiding layers has no solder filled therein. Therefore, the connection between the braiding layers of the cable and the PCB is not reliable. When the micro-coaxial cable connector assembly is subject to an external force, the connection between the braiding layers of the wires and the PCB is easy to break and thus the grounding effect is adversely affected
Hence, an improved method for soldering braiding layers of a micro-coaxial cable to a printed circuit board is desired to overcome the disadvantages of the related art.
The main object of the present invention is to provide a method for stably and conveniently soldering braiding layers of a micro-coaxial cable to a printed circuit board, thereby ensuring a reliable grounding effect.
To achieve the above-mentioned object, an improved method for connecting braiding layers of a micro-coaxial cable to a printed circuit board is disclosed by the present invention, wherein the micro-coaxial cable consists of a plurality of individual wires each including a core conductor, an inner insulator coated over the core conductor, a braiding layer surrounding the inner insulator, and an outer insulator coated over the braiding layer. The method comprises the steps of: exposing the braiding layers of the wires; providing a substrate having a thick layer of fusible element thereon; and arranging the braiding layers onto the thick layer of fusible element while providing enough energy such that molten fusible element is substantially filled in interstitial space between the braiding layers of adjacent individual wires.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of the present embodiment when taken in conjunction with the accompanying drawings.